All below said is valid for non-muslims. I believe it applies to muslim citizen of non-islamic countries as well.
1. Divorce should be recognizable in the country where the marriage was registered.
2. If both of them have different nationality and the marriage was registered in third country, check if it has been properly legalized in the countries of citizenship of both of them respectively. If not, they might be still considered single by their respective countries.
3. If they are citizen of the same country, they should resolve the matter in the country of their citizenship.
4. In all cases don't bother getting a divorce from Qatari authorities. Qatar is not a member of the Hague Convention, and documents from Qatar require full consular legalization, and even so, might be not recognized by the country of citizenship.
The right place to ask is the consular department of the embassy of the country of citizenship of your friend.
All below said is valid for non-muslims. I believe it applies to muslim citizen of non-islamic countries as well.
1. Divorce should be recognizable in the country where the marriage was registered.
2. If both of them have different nationality and the marriage was registered in third country, check if it has been properly legalized in the countries of citizenship of both of them respectively. If not, they might be still considered single by their respective countries.
3. If they are citizen of the same country, they should resolve the matter in the country of their citizenship.
4. In all cases don't bother getting a divorce from Qatari authorities. Qatar is not a member of the Hague Convention, and documents from Qatar require full consular legalization, and even so, might be not recognized by the country of citizenship.
The right place to ask is the consular department of the embassy of the country of citizenship of your friend.